How can I limit the number of rows in Oracle

I have got a query that returns thousands of rows but I'm only interested in the first 20 records. In mysql I can limit the returned data (and thus the network traffic) with the LIMIT start,number clause, where start is the starting row and number is the number of rows that I want to see.

Is something similar possible in Oracle as well?

Answer:

Oracle has a system attribute ROWNUM for each record returned. A query that only returns the first 20 records would look like the one in the example.